The present invention relates to implantable medication infusion pump devices and, more particularly, to a device of this type which may be injected into the body of an animal. The invention also relates to apparatus for injecting the infusion pump device and to a method therefor.
It is known that infusion of growth hormones produced by recombinant DNA and possibly other drugs provide benefit in animals such as increased quantity of milk production in cows, larger growth of the animals to increase weight and edible meat, a reduced fat content of meat and an improved feed efficiency for the animals, among other things. Presently, such drugs are injected into the animals as often as once a day by syringe/needle bolus injections. Such procedures are time consuming and costly.
In my copending United States patent application entitled "Implantable Medication Infusion Device and Bolus Generator Therefor", Ser. No. 162,766 filed Mar. 1, 1988, I describe an implantable medication infusion pump device of the continuous flow type which is surgically implanted into the body cavity of an animal such as a cow or a hog. The device described therein is an inexpensive drug infusion device made of non-metallic parts, primarily of molded plastic and rubber parts. The device is implanted next to the skin of the animal such that it may be refilled by percutaneous syringe/needle injection. It has a drug capacity which lasts several months and therefore requires refilling only once ever several months. Pressurized air or inert gas is used as a propellant acting upon a medication reservoir for forcing the drug out of the device to the infusion site. The reservoir comprises a flexible bladder restrained from elastically expanding by the pump structure so as not to add contraction forces of a stretched bladder wall to the pressure generated by the compressed air or inert gas, thereby rendering the force on the medication essentially constant. A flow restrictor is incorporated in an outlet of the device to regulate the drug dosage which is delivered to the infusion site by a catheter connected to the outlet.
The aforedescribed invention of my copending application avoids the nuisance, expense and high possibility of infection attendant with daily injections of growth hormones for hundreds of days. However, that device does require a trained surgeon for implanting the device. The costs of such surgical implantation may significantly reduce the cost benefit derived from the medication dosages.